US3732689A

US3732689A - Compound diesel engine of rotary-piston type

Info

Publication number: US3732689A
Application number: US00146028A
Authority: US
Inventors: H Tado; T Morimoto
Original assignee: Yanmar Diesel Engine Co Ltd
Current assignee: Yanmar Co Ltd
Priority date: 1971-05-24
Filing date: 1971-05-24
Publication date: 1973-05-15
Anticipated expiration: 1990-05-15

Abstract

A compound internal-combustion engine of rotary-piston type having two sets of juxtaposed rotary-piston engine units each including a housing with a bilobed epitrochoidal or approximately epitrocoidal inner surface and a substantially triangular shaped rotor rotatably mounted on an eccentric portion of a shaft journaled in said housing with the apexes thereof adapted to be moved in sliding contact with the inner surface of the housing. One of the engine units works as an internal-combustion engine and the other unit serves as a compressor. The shaft of the second unit runs in the same direction as that of the first unit but at twice the speed, and a rotary control valve is installed between the two units so that air compressed in the second unit is supplied syncronously to the rotation of the first unit.

Description

fay 15, 1973 ilnite States Patent [191 Tado et all.

[541 COMPOUND DIESEL ENGINE 0F ROTARY-PISTON TYPE Primary Examiner-Carlton R. Croyle Assistant ExaminerMichael Koczo, Jr. Attorney- Stevens, Doris. Miller & Mosher [75] Inventors: Hiroshi Tado, Suita; Teruo Morimoto, Nagahama, both of Japan ABSTRACT [73] Assignee: Yanmar Diesel Engine Co., Ltd.,

Osaka, Japan A compound internal-combustion engine of rota piston type having two sets ofjuxtaposed rotary-piston engine units each including a housing with a bilobed epitrochoidal or approximatel 22 Filed: May 24,1971

Appl. No.: 146,028

y epitrocoldal inner surce and a substantially triangular sha rtfr m wm h m mm fl e d h m a mu .l W na 0 p6 U S Cl 123/805 rotatably mounted on an eccentric 51 lm. CI..........................F02b 41/02, F02b 53/08 journaled in Said housing with m [58] Field Of Search..................l23/8.43, 8.29, 8.41, da ted to be moved in sliding ontact 1 /8- 119 6O/15, 39-43 surface of the housing. One of the engine units works as an internal-combustion engine and the other unit serves as a compressor. The shaft of the second unit runs in the same direction as that of the first unit but at twice the speed, and a rotary control valve is installed between the two units so that air com the second unit is supplied syncronousl tion of the first unit.

[5 6] References Cited pressed in y to the rota- 1 Claim, 14 Drawing Figures 7 III IIIIi I'll PATENTED 51975 3. 732 689 sum 1 0r 5 ATTORNEY! PATENIEUNAYWBB 3,732,689

SHEET 2 [IF 5 PATENTED 3,732,689

SHEET 5 OF 5 COMPOUND DIESEL ENGINE OF ROTARY-PISTON TYPE This invention relates to a rotary-piston engine, and more specifically to the construction of so-called orbiting rotary-piston engine.

A rotary-piston engine of the construction above re ferred to usually uses a substantially multisided rotor (to be hereinafter called a rotor) which is mounted offcenter on the output shaft of the engine and held in a housing having a multilobed, or more commonly a bilobed, epitrochoidal inner geometry, and which rotates with its apexes in continuous sliding contact with the curved inner surface of the housing. In an engine of this type wherein given spaces are provided as working chambers between the inner surface of the housing and the flanks of the rotor, the volume of the working chamber in which the rotor as a rotary piston is at its top dead center for maximum compression of the charge is very large as compared with the volume in a reciprocating-piston engine, and it is difficult to attain a desirable compression ratio of the charge.

In an effort to eliminate the foregoing disadvantage, it has been proposed to juxtapose a pair of rotarypiston engine units of the same design and cause them to run in the same direction at the same speed, in such a manner that one of the engine units serves as a compressor and supplies compressed air to the intake port of the other engine unit and, at the same time, the exhaust from the engine unit is returned to the compression unit for reexpansion so that the compressor unit plays the role of a rear-stage expansion unit, too. Engines of the construction described, known as compound internal-combustion engines of rotary-piston type, have been known in the art from the published specifications of Japanese Patent Publication Nos. l2554/1964, 681/1965, 11922/1966 and 11321/1969.

The ratio of the stroke volume of the engine unit (hereinafter called the first unit) to that of the compressor unit (hereinafter called the second unit) is usually l 2 or upwards where the Diesel cycle is employed. This is because a volume ratio between 1 2 and 1 3 is necessary in order to attain a sufficient compression ratio for a proper Diesel cycle and provide a desired space where a good combustion efficiency is attained in the maximum compression state with the rotor of the first unit at its top dead center.

If the stroke volume ratio of the first and second units is 1 2, it means that, provided that the both units have epitrochoidal housings of the same profile (hereinafter called the rotor housings), the width of the rotor housing for the second unit must be twice as large as that of the first unit. If the both rotor housings of the first and second units are to have the same width, then the epitrochoidal profile of the second unit will have to be much larger than that of the first unit. Whichever method may be resorted to, the second unit has to be bulkier than the first unit, thus necessitating a large overall construction and an increase in weight as inevitable shortcomings.

The present invention is proposed to eradicate those shortcomings of the compound engines above described. It enables the rotor of the second unit of such an engine to run in the same direction as that of the first unit but twice as fast as the latter so that the first unit in its intake stroke can take in a volume of air about twice as large as the stroke volume of the second unit.

In this manner working spaces are secured which render it possible to expect adequate combustion of the charge in the Diesel cycle while restricting any increase of the overall dimensions of the structure and minimizing its weight gain.

The invention will be more fully described hereunder in conjunction with the accompanying drawings showing an embodiment thereof. In the drawings:

FIG. 1 is a sectional view taken along the line BB of FIG. 2 illustrating an embodiment of the invention;

FIG. 2 is a sectional view taken along the line A-A of FIG. 1; and

FIGS. 3 through 14 are views explanatory of the rotatory positions which are assumed at sequential moments by a pair of rotors accommodated in an engine according to this invention.

Referring to FIGS. 1 and 2, a rotor housing common to the first and second units is generally indicated at 1, and there are shown a pair of rotors 3, 5 and output shafts 7, 9 which have

eccentric portions

7a, 9a, respectively. In a side housing 15 are secured gears 1 1, 13, which are in mesh with inner gears 17, 19 mounted, respectively, on the rotors 3, 5, the gear ratio being 2 z 3. To one ends of the shafts 7, 9 are fixed

gears

21, 23, which are in communication with each other through an intermediate gear 25. The gear ratio of the gear 21 mounted on the first unit and the gear 23 on the second gear is 2 l, the shaft 9 of the second unit makes two revolutions while the shaft 7 of the first unit completes one revolution. FIG. 1 shows a fresh-air intake port 27, a fresh-air supply port 29 through which the fresh-air from the port 27 is supplied to the first unit, and a fresh-air filling port 30 for the first unit. A rotary control valve 31 is formed with a passageway 33. The rotating motion of the control valve is transmitted by means of a serrated belt 39 which is engaged with a pulley 37 fixedly mounted on the shaft 7 of the first unit and a pulley 35 on the shaft end of the control valve 31. Thus, the valve 31 is driven in the same direction and at the same speed as the shaft 7 of the first unit, and the rotation of the valve 31 is synchronized with that of the shaft 7 of the first unit so that the passageway 33 continuously changes the cross sectional area of the fresh air passage between the fresh-air supply port 29 and filling port 30 and, at certain intervals, shuts off the passage between the two ports. Numeral 41 indicates a hot-gas discharge port, 43 a hot-gas inlet port communicated with the discharge port via a passage, 45 an exhaust port for waste gases, and 417 a fuel injection valve. Arrow marks show the revolving direction of the engine.

Next, the operation of the engine according to the present invention will be explained with reference to FIGS. 3 to 14. Throughout these figures, the unit at left is the second unit and the one at right is the first unit, and arrow marks indicate the revolving direction. For convenience of illustration, the operation in connection with only the chamber V of the first unit will be followed. FIGS. 1 and 3 show the engine in such a positional relationship that one flank of the rotor 5 of the second unit is on top of the hot-gas inlet port and one flank of the rotor 3 of the first unit on top of the freshair filling port. Here the rotors of the first and second units and the passageway 33 through the control valve 31 are so positioned that the passageway does not communicate the fresh-air supply port 29 to the fresh-air filling port 30. In this state intake of fresh air into the chamber V is yet to be started. FIG. 4 shows the passageway 33 of the control valve 31 about to establish a communication between the fresh-air supply port 29 and the filling port 30. At this time, one of the apexes of the rotor 5 of the second unit is at a point past the fresh-air supply port. In FIG. 5, fresh air taken in through the intake port 27 of the second unit is led through the passageway 33 of the control valve 31 into the chamber V, of the first unit. The intake from the fresh-air intake port 27 into the chamber V, of the second unit has been completed. In continuation from the state shown in FIG. 5, the volume of the chamber V of the first unit keeps on expanding with the decrease in the volume of the chamber V of the first unit as shown in FIG. 6, so that the chamber V is continuously charged with fresh air via the passageway 33 through the control valve 31. At this point the cross sectional area of the passage through the passageway 33 of the control valve 31 approaches a maximum value. Meanwhile, the chamber V of the second unit begins intake and, with the expansion of the chamber V the intake progresses throughout the conditions illustrated in FIGS. 7 to 9. FIG. 9 shows the chamber V of the second unit in its minimum volume and the passageway 33 through the control valve 31 closed out of communication with the fresh-air filling port 30, thus completing the supply of fresh air from the chamber V of the second unit into the chamber V of the first unit. During the process from FIG. 9 to FIG. 10 the chamber V of the first unit shows some pressure drop because the passageway 33 of the control valve 31 remains closed against admittance of fresh air and, moreover, the chamber keeps on expanding for the limited period of time. However, in a slightly advanced state from FIG. 10, one of the apexes of the rotor of the second unit passes the freshair supply port 29 and begins to open the passageway 33 of the control valve 31. For some time during the progress from FIG. 10 to FIG. 11 the passageway 33 of the control valve 31 is open and the fresh-air intake port 27 of the second unit also remains open. Fresh air admitted into the chamber V of the first unit during this period then flows into the chamber V of the second unit and tends to flow back to the outside through the fresh-air intake port 27. This period is extremely short, however, and the amount of air that flows out of the intake port 27 is negligibly small. FIGS. 11 to 14 illustrate how the chamber V of the first unit is increasingly supercharged with air from the chamber V of the second unit. In FIG. 14 the intake in the chamber V is over and compression starts in the same chamber. Thus, because the shaft 9 of the second unit makes two revolutions while the shaft 7 of the first unit completes one revolution, it follows that if the stroke volume of the second unit is equal to that of the first unit, the first unit will be charged with approximately twice as much air as the stroke volume of the first unit. With the engine of the construction so far described, it is possible effectively to realize a Diesel cycle by choosing an appropriate volume ratio without materially increasing the stroke volume of the second unit as compared with that of the first unit. It should be clear to those skilled in the art that the present invention which permits reduction in size of the second unit will provide a small-size, compact and lightweight engine. Also, as will be appreciated from the foregoing description, the high pressure gases after combustion in the first unit are led into the two chambers of the second unit where the gas energy is recovered therefrom. Therefore, as compared in the conventional arrangement wherein the rotors of the first and second units are driven in the same rotational speed, the rotor 5 of the second unit according to this invention requires no special consideration for cooling; it may be simply an air-cooled rotor. This is another advantage of the invention, though of secondary importance.

The foregoing description has been made on the assumption as already stated at the beginning of the explanation of the operation that, when the positional relationship is such that one flank of the rotor of the second unit is above the top end of the hot-gas inlet port and one flank of the rotor of the first unit is above the top end of the fresh-air filling port, then the rotors of the first and second units and the passageway of the control valve are so positioned with respect to one another that the passageway of the control valve is closed to shut off the communication between the fresh-air supply port and filling port. It is also possible, of course, that one flank of the rotor of the first unit may come to the front or back of the top end of the fresh-air filling port. If such is the case, it is needless to say that the synchronized action of the control valve with the rotation of the shaft of the first unit will have to be accordingly modified and set to a proper value. Driving of the control valve may be accomplished by either shaft end of the first or second unit. If the control valve is to be driven by the output shaft of the second unit, it is only necessary to choose a speed ratio of l 2 for the valve and the shaft of the second unit. As for the driving means, gear and chain-drive systems may be employed as well without departing from the spirit and scope of the present invention. The arrangement shown in FIG. 2 is merely illustrative of the principle of the invention.

What is claimed is:

1. A compound diesel engine of the rotary piston type, consisting of two sets of juxtaposed rotary-piston engine units each including a housing with a bilobed epitrochoidal or approximately epitrochoidal inner surface and a substantially triangular shaped rotor rotatably mounted on an eccentric portion of a shaft journaled in said housing with the apexes thereof adapted to be moved in sliding contact with the inner surface of the housing, one of the engine units working as an internal-combustion engine and the other serving as a compressor,

a filling passage connecting a fresh-air filling port of said internal combustion engine with a fresh-air supply port of said compressor,

a return passage connecting a combustion gas discharge port of said internal combustion engine with a combustion gas inlet port of said compressor,

characterized in that the shaft of said compressor rotates in the same direction as that of the internal combustion engine but at twice the speed of said internal combustion engine, and

a rotary control valve installed in said filling passage, said valve being synchronized with one of said shafts such that said rotary slide valve begins to open when one apex of the rotor of the compressor moves past the fresh-air supply port and closes when the rotor of the compressor is at the intersection dead center with respect to the fresh-air supply port and the combustion gas inlet port whereby in one suction stroke of the internal combustion engine, a volume of air corresponding two times of suction and compression strokes of the compressor is filled in the working chamber of the internal combustion engine pertaining to such suction stroke.

Claims

1. A compound diesel engine of the rotary piston type, consisting of two sets of juxtaposed rotary-piston engine units each including a housing with a bilobed epitrochoidal or approximately epitrochoidal inner surface and a substantially triangular shaped rotor rotatably mounted on an eccentric portion of a shaft journaled in said housing with the apexes thereof adapted to be moved in sliding contact with the inner surface of the housing, one of the engine units working as an internalcombustion engine and the other serving as a compressor, a filling passage connecting a fresh-air filling port of said internal combustion engine with a fresh-air supply port of said compressor, a return passage connecting a combustion gas discharge port of said internal combustion engine with a combustion gas inlet port of said compressor, characterized in that the shaft of said compressor rotates in the same direction as that of the internal combustion engine but at twice the speed of said internal combustion engine, and a rotary control valve installed in said filling passage, said valve being synchronized with one of said shafts such that said rotary slide valve begins to open when one apex of the rotor of the compressor moves past the fresh-air supply port and closes when the rotor of the compressor is at the intersection dead center with respect to the fresh-air supply port and the combustion gas inlet port whereby in one suction stroke of the internal combustion engine, a volume of air corresponding two times of suction and compression strokes of the compressor is filled in the working chamber of the internal combustion engine pertaining to such suction stroke.